Ubuntu Grub 修復

sudo mkdir /mnt
sudo mount /dev/sdXn /mnt

sudo mount --bind /dev /mnt/dev
sudo mount --bind /dev/pts /mnt/dev/pts
sudo mount --bind /proc /mnt/proc
sudo mount --bind /sys /mnt/sys

sudo chroot /mnt

grub-install /dev/sdX
(if not chroot : grub-install --root-directory=/mnt/ /dev/sdX)

grub-install --recheck /dev/sdX

update-grub

exit
sudo umount /mnt/sys
sudo umount /mnt/proc
sudo umount /mnt/dev/pts
sudo umount /mnt/dev
sudo umount /mnt

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other command:
sudo fdisk -l
sudo parted /dev/sdX print
sudo lsblk